Induction coil



Sept. 15, 1959 2,904,763

R. B. HARRUFF INDUCTION COIL Filed April 26, 1956 2 Sheets-Sheet 1 n" I I I! G g BY IMBFBT B. Mam/ f I 11 In h 1115 ATMBNH Sept. 15, 1959 R. B. HARRUFF 2,904,763

INDUCTION COIL Filed April 2a, 1956 2 Sheets-Sheet 2 a 8081537 B. Ham/f a VBY M Hi5 ATTORNEY 6 IN VEN TOR.

United States Patent Ofiice 2,904,763 Patented Sept. 15, 1959 INDUCTION COIL Robert B. Harruif, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 26, 1956, Serial No. 580,851

4 Claims. (Cl. 336- 182) This invention generally relates to induction coils and is more particularly concerned with coils of the type used in ignition systems for internal combustion engines.

it is well known the ratio of horsepower output per unit Weight of the modern internal combustion engines is constantly being increased. This increase is largely accomplished by increasing either or both the engine compression ratio and the speed of revolutions. When either of these factors is increased, the demands imposed upon the ignition system to cause proper ignition of the mixtures within the cylinders of the engine are correspondingly increased. This means the power output of the electrical components of the ignition system must be increased over shorter ignition periods of time.

The present invention is directed to an ignition coil which will satisfy the increased igniton requrements of the modern internal combustion engine. This is accomplished by combining the various windings and magnetic iron parts within the metal container of the ignition coil in a manner to provide an improved ignition coil which will operate in an ignition system to satisfactorily ignite the combustible mixtures within the engine cylinders without an unusual amount of electrical impulses which will interfere with the surrounding radio equipment.

The type of ignition coil herein contemplated includes a closed circuit magnetic core which is of the hollow rectangular type that has a primary winding and a secondary winding inductively coupled on one leg of said core and a single primary winding on the other leg of the corefwhich primary windings are arranged so the fluxes induced in the core legs by the primary windings are in opposition to each other when the primary windings are energized. It is an object of the present invention to include auxiliary magnetic metal in this coil, which metal is arranged and spaced from each of the core legs to provide a path for a portion of the flux when the fluxes are in opposition to each other.

It is another object of the present invention to provide aset of supplemental magnetic metal parts in an ignition 6011 which parts consist of laminae of magnetic metal that are spaced from and partially surround the legs of acore that has a closed magnetic circuit, so the fluxes which are induced in the legs of the magnetic core by a 'pair' of primary windings may pass through the supplemental magnetic metal when the fluxes are opposed to each other. In carrying out this object, it is another object of the present invention to enclose the coil parts in a metallic container so as to provide a coil which has an increased electrical output and which coil will not interfere with surrounding radio equipment.

A further object of the present invention is to provide an improved ignition coil structure and ignition circuit therefor wherein the structure of the coil includes: a hollow rectangular type magnetic core whereon a primary winding is positioned about one of the legs of the core and a primary and secondary winding is positioned about another leg of said core and a plurality of bundles of metal laminae having a C-shaped cross-section shape are arranged to embrace in spaced relation both core legs to provide a path for a portion of the magnetic flux in said core when the fluxes in said core legs oppose each other as when a pair of contacts open and close the individual circuits to said primary windings simultaneously or when the circuit to the primary winding that is wound on the same core leg as said secondary winding is opened and closed by a breaker point slightly before the circuit to the other primary winding.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure l is a top plan view of an ignition coil embodying the present invention.

Figure 2 is a cross-sectional view of the'coil according to the present invention taken along line 22 in Figure 1.

Figure 3 is an enlarged view of the terminal for the coil taken along line 3-3 in Figure 1.

Figure 4 is a diagrammatic top view of the magnetic iron parts of the coil shown in Figure 1.

Figure 5 is a diagrammatic side view of parts of the coil in Figure 1 showing the magnetic iron arrangement and the arrangement of the coil windings.

Figure 6 diagrammatically shows an ignition circuit for the coil in Figure l.

Referring to Figure 2, the coil 20 has a porcelain base 21 which is provided with suitable sockets for positioning the core 22, the primary coil windings 24 and 26, and the secondary coil winding 28 as will be hereinafter described.

The core 22 is preferably formed of a plurality of magnetic metal strips which are laminated and arranged to provide a closed magnetic circuit. This core 22 is shown as a hollow square or rectangle and has primary coil windings 24 and 26 and secondary windings 28 surrounding the legs or sides of the core 22 as shown in Figures 2 and 5. The primary coil winding 26 is wound on the right leg of the core 22 as shown in Figure 2. This winding 26 is spaced from the magnetic metal laminae which forms the right leg of core 22 and is comprised of the conventional wire layers alternating with paper layers on a non-conducting tube. The secondary coil winding 28 is spaced from the left leg of the, core 22 and is surrounded by the primary coil winding 24. Both the secondary winding 28 and the primary Winding 24 are of conventional construction. It is clearly apparent the coil windings can be wound on the core 22 after the laminations are assembled to form the hollow square structure or the coil windings may be separatelywound and placed on the laminations which form the legs of the core and then the remainder of the core 22 can be assembled.

The coil 20 is also provided with a suitable cap 30 and a container 32. The cap 30 has suitably located and shaped lugs 34 which are arranged to embed themselves in the paper of the coil windings to maintain the windings in position. The parts of the coil preferably are assembled as disclosed in the Hartzell Patent 2,512,796 which is assigned to the assignee of the present invention and sets forth how the container which is oil filled may have a hermetic seal maintained between the cap 30 and container 32 and how the component parts of the coil are constantly maintained in position because of the core receiving socket in the cap 30 and the pad 36 in the base of the container.

The coil 20 in Figure 2 has a spring 38 which is arranged to maintain the core 22 in position on the base 21 and to form electrical contact with the core. This spring 38 is preferably formed of a flat piece of metal which is curved as shown to have its ends contacting the. core, and its mid-portion. contacting the cap. The spring 38 also has a struck-out central portion 40 which is forced downwardly by the terminal screw 41 to engage the material of the core to form an electrical connectiontherewith, As was set forth in the Hartzell patent sup f e leads f t e econda y oil nd n 28.is electrically connected to the material of the core 22 so an electrical circuit is completed between the screw 41 and one end' of the secondary winding 28', The other end of the secondary winding is connected to the primary coil winding 24 as shown in Figure 6.

In Figure 3 of the drawings, the connection between the leads of the coil windings and the terminal in the cap 30 is as shown. Each of the terminals are sealed in the material of the cap 30 by a method which is not part of the present invention. Each of the terminals 42, 50, 52 and 54 are connected with the proper end of the. leads of the coil windings by a clip 44. To accomplish this connection, the clip 44 is first suitably secured to the lead end 46 of the coil windings as by soldering or Welding. After the various parts of the coil including the core 22, end ofthe coil windings 24, 26 and 28 and the base 21 are in position and the inverted cap as disclosed in the .Hartzell patent, supra, the clips 44 are secured to the terminals as by soldering orwelding. After the electrical connection is established between the terminals and leads, the laminated iron parts 48 and 49 which will be hereinafter described, are positioned, and the container 32 is positioned, over the inverted cap and sealingly secured thereto as set forth in the Hartzell patent, supra.

In Figures 4 and S of the drawings, the shapev and location of the supplemental iron parts 48 and 49; are most clearly shown. Thesupplemental iron parts 48 and 49' preferably comprise a laminae of magnetizable sheet iron which is longitudinally slitted in a manner shown in the Hartzell Patent 1,883,905. These laminae are preferably C-shaped in cross-section as shown in Figure 4 and extend preferably over a substantial length of the legs of the core which are surrounded by the primary windings 24' and 26 and will provide a path for a portion of the flux which is induced in the core 22 when the fluxes in the right and left legs are in opposition to eachother. It is apparent that the laminae may be other than C.- shaped and, if desired, need not be slitted as set forth.

As shown in Figure l, the coil has terminals 42, 50, 52, 54 and 56. These terminals are connected to similarly numbered and suitably located junctions as shownin the wiring diagram of Figure 6.

The ignition distributor which is used with the coil of the present invention and is not shown preferably hastwo sets of breaker points. 58 and 60 which are. operated by the same cam 62. The cam 62 and the breaker points 58'and 60 are conventional construction and arearra-nged .so that the, contacts 53 and 60 preferably close at approximately the same time. However, if desired and for the purposes of mechanical design it may be advisable to have contacts 58 close slightly before contacts. 60 so that contacts 58'may open before contacts 60 open. When the contacts 58 and 60 close, current will pass. through each of the primary windings 24 and 26 and cause a magnetic fluxto be generated in two circuits. The coil windings 24 and 26 are wound so the direction of the flux through the iron core will be as indicated by arrows.

64; and, 66. It is believed that these fluxes will flo'w through a magnetic circuit which consists of a portion of the iron core 22, the supplementary iron 48, and 49 and a relatively large air gap. The path of the. fluxes is shown by the dotted lines 68 and '70. It will be noted that the path. in the right and left legs of the core 22 are in opposition to each other when the contacts 58. and 60 are closed.

As. heretofore stated, contacts 58 preferably open before. contacts 60 open. When contacts 58. open, the flux shqwn by the dotted lines 63, which was generated by the. current. in primary 24-, collapses. Therefore, the

course of the flux generated by primary 26 changes from that shown by the dotted line 70 to the relatively easier path through the core as shown by arrows 72. Thus, the

flux in the leg of the core 22 passing through the secondary winding 23 changes rapidly from a relatively high value in one direction to a relatively high value in the other direction. This relatively rapid and large total change in flux in this portion of'the iron core generates a high voltage pulse in the secondary winding 28. After this high voltage pulse is produced, contacts 60 open permitting the remaining flux to. collapsewhich restoresthe, system to its original condition. This. sequence of'eyents is then repeated.

This system, when using the same, amount of. current through each set of contacts as used in the ignition systems heretofore known, will produce a greater output than the coils of conventional cross-section. This is because energy is stored in the magnetic iron and air gaps of two circuits while the contacts are closed. This energy serves to generate voltage in a single secondary when the COD-1 tacts 53 open.

The advantages of the use of the supplementary iron are several. It is to be noted that if the coil structureas shown in the drawings is used without supplementary metal, then the flux that is produced when the contacts are closed must follow a considerably longer air path. With supplementary iron it has been found that fewer ampere turns of wire are required in the primary wind: ing to produce the same amount of flux in the core iron when both contacts are closed. This in turn means. that fewer turns on the secondary winding are required to have the same secondary to primary turns ratio.

Another advantage of the supplementary iron is that it will reduce radio interference. Also it will enable the coil parts to be included in a metallic container. If the, coil shown were used without supplementary iron, the. metal container itself would be in the magnetic. field. Then when the field collapses, as described before, electrical currents would be generated in the container, creating substantial losses in the circuit which would diminish the output of the system. A metal container is desirable because it is low cost, durable, and further reduces. radiov interference. If this coil without supplementary metal is located near other metal parts such as the engine itself, then the operational characteristics of the coil will be. considerably affected. This is extremely undesirable in that in the modern-day ignition systems the operational outputs of the. coil must be precisely determined so. that the proper operation of the engine will be accomplished. The. resistors 74 and 76, the condensers 78. and 80, the battery 82 and the ignition switch 84 are conventional. The resistors 74 and 76. may be included, if desired, and may be. ballast resistors in which the resistance values change appreciably with temperatures to give more desirable performance characteristics of the ignition sys-v tem. Further, ifit is desired, these resistances. may be shorted out or bypassed while the engine is being cranked so that the output of the coil will be considerably; in.- creased.

As noted in Figure 4, the supplementary iron parts, 49 and 48. are C-shaped. When the metal parts are thus formed, the greatest amount of area possible will be presented to embrace legs of the core which. pass through the coil windings 24 and 26, respectively. This arrange.- ment will provide a coil with the-maximum output for the amount of material used.

While the embodiment of the present invention as herein disclosed constitutes, a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows;

1. In an induction coil, the combination comprising; a rectangularly-shaped magnetic core having a central opena ing, a pair of primary coil windings on opposite sides of said rectangular core and wound in adirection to produce opposing magnetic fluxes in said core when both of said coil windings are connected to an electric current source, a secondary coil winding positioned in inductive relation with one of said primary windings, and a means comprising a pair of G-shaped magnetic metal laminae located longitudinally of said core and spaced from the said sides of the core on which the primary windings are wound for providing an alternate path for the flux which is operative only when said fluxes are opposing each other.

2. An induction coil comprising, a metal container, a hollow rectangular shaped metal core in said container having first and second legs located in the same plane and substantially parallel to the side walls of said container, a primary coil winding and a secondary coil winding on said first leg, 2. second primary winding on said second leg, said primary windings being wound on said legs in such a direction that the magnetic flux induced respectively in each leg when said windings are energized flows through said legs in opposing directions, a first member formed of laminated metal material having a substantially C-shaped cross section located between said container and said first leg with said member partially enclosing said first leg and extending substantially parallel thereto, and a second member formed of laminated material having a substantially C-shaped cross section located between said container and said second leg with said second member partially enclosing said second leg and extending substantially parallel thereto.

3. An induction coil comprising, a magnetic core having a pair of legs connected by a pair of intermediate sections to form a unitary core and a closed magnetic circuit, a first primary winding and a secondary winding on one of said legs, a second primary winding on the other of said legs, said primary windings being wound on said legs in such a direction that the magnetic flux induced respectively in each leg when said windings are energized flows through said legs in opposing directions, a first laminated metal part spaced from one of said legs, and a second laminated metal part spaced from the other of said legs, said metal parts providing an alternate flux path for flux induced in said legs when said fluxes are opposing.

4. In an induction coil, the combination comprising; a rectangular shaped magnetic core having a central opening, a pair of primary coil windings on opposite sides of said rectangular core and wound in such a direction as to produce opposing magnetic fluxes in said core when both of said coil windings are connected to an electric current source, a secondary coil winding positioned in inductive relation to one of said primary windings, and a means comprising magnetic metal laminae located longitudinally of said core and extending in spaced relation to said sides of the core for providing paths for the fluxes in said core in addition to the path provided by said core.

References Cited in the file of this patent UNITED STATES PATENTS 1,036,445 Burnham Aug. 20, 1912 1,358,901 Varley Nov. 16, 1920 1,553,829 Mallory et al Sept. 15, 1925 1,598,486 Mallory Aug. 31, 1926 FOREIGN PATENTS 295,502 Great Britain Aug. 16, 1928 

